This invention relates generally to switching circuitry and more particularly, it relates to a switch circuit for selectively driving a LED display device at either a dim or bright intensity. The switch circuit of the present invention has particular applications in LED display devices used with the control panels of an aircraft cockpit so as to have the capability of driving the display devices at dim and bright levels of intensity. The bright intensity is required in the daylight hours when the brightness of the sunlight into the cockpit may interfere with visibility of display devices. On the ether hand, the dim intensity is used in the evening or nighttimes when there is no outside interference thereby reducing power consumption and prolonging the useful life of the display devices.
It is the user who generally supplies input voltages to the switch circuit. Generally, these input voltages may vary over a wide range for illuminating the display devices either at the dim or bright intensity. The switch circuit is required to have the ability of providing and maintaining either the dim intensity when a first range of the input voltages is supplied or the bright intensity when a second range of the input voltages is supplied.
Accordingly, it would be desirable to provide a switch circuit for selectively driving a LED display device at either a dim or bright intensity in response to varying input voltages. It would also be expedient to provide a switch circuit which operates in a highly efficient manner and has a relatively low power consumption.